1. Field of the Invention
The present invention relates to a record medium such as a digital audio compact disc with a subcode in association with main digital data such as audio data and visual data, a reproducing apparatus thereof, and a reproducing method thereof.
2. Description of the Related Art
In a CD (compact disc) reproducing apparatus that reproduces audio information from a CD, various types of data are displayed corresponding to information reproduced from the disc so as to improve the operability of the apparatus. As an example of the data, a program number (so-called track number) and time information assigned thereto are displayed. Such information is recorded to a sub-code of channel Q (that will be described later).
As shown in FIG. 1, a CD 101 has a hole 102 at the center thereof. A read-in region 103, a program region 104, and a read-out region 105 are successively formed around the hole 102. The read-in region 103 is a program management region in which TOC (Table of Contents) data is recorded. In the program region 104, program data is recorded. The read-out region 105 is a program end region. Audio data is recorded in the program region 104 of the audio CD. Time information and so forth of the audio data are managed in the read-in region 103. When audio data has been completely read from the program region 104 and a pickup of the apparatus has reached the read-out region 105, the CD reproducing apparatus completes the reproducing operation of the CD.
FIG. 2 is a block diagram showing an example of the structure of the CD reproducing apparatus. The CD reproducing apparatus reads audio data from the CD 101 with a pickup 112. A digital signal processing circuit 116 processes the audio signal and outputs reproduced data to a digital signal output terminal 125 or analog signal output terminal L and R.
The pickup 112 has an optical device (such as an objective lens), a semiconductor laser, a four-divided detector (that receives rays reflected by the CD 101), and so forth. When an output signal of the four-divided detector is calculated, an RF signal, a focus error signal, and a tracking error signal are formed. The RF signal is supplied to an analog waveform shaping circuit 114. The focus error signal is supplied to a focus servo circuit 120. The tracking error signal is supplied to a tracking and thread servo circuit 121.
The analog waveform shaping circuit 114 shapes the waveform of the RF signal received from the pickup 112 and supplies the resultant signal to a synchronous detecting circuit 115 and a clock signal generating circuit 117. The clock generating circuit 117 generates a reproduced clock signal that corresponds to the RF signal received from the analog waveform shaping circuit 114 and that synchronizes with the RF signal. The clock signal generating circuit 117 supplies the reproduced clock signal to the synchronous detecting circuit 115, the digital signal processing circuit 116, and a rotation servo circuit 122. The synchronous detecting circuit 115 detects a frame synchronous pattern from the RF signal corresponding to the reproduced clock signal received from the clock signal generating circuit 117. The synchronous detecting circuit 115 supplies the detected signal of the frame synchronous pattern to the digital signal processing circuit 116.
The digital signal processing circuit 116 performs a reproducing process for the RF signal received through the synchronous detecting circuit 115. In reality, the digital signal processing circuit 116 performs an EFM demodulating (Eight-Fourteen Demodulating) process, an error-correction-code decoding process, an error interpolating process, and so forth. To perform these processes, the digital signal processing circuit 116 uses the reproduced clock signal received from the clock signal generating circuit 117 and a reference clock signal received from a crystal oscillator 119. A digital audio signal of left and right channels is supplied from the digital signal processing circuit 116 to the digital output terminal 125. In addition, the digital audio signal is supplied to a D/A converter 123. The D/A converter 123 converts a digital signal into an analog signal. An audio amplifier 124 amplifies the analog audio signal received from the D/A converter 123 and outputs the amplified analog signal to the analog signal output terminals R and L.
The digital signal processing circuit 116 is connected to a sub-code detecting circuit 118. The sub-code detecting circuit 118 detects data of channels P and Q of a sub-code from the digital signal received from the digital signal processing circuit 116. A microprocessor 126 detects time information from the detected data of channels P and Q and controls the tracking and thread servo circuit 121 corresponding to the detected timing information.
A focus drive signal is supplied from the focus servo circuit 120 to the pickup 112. The focus servo circuit 120 performs a focus servo operation for the pickup 112 so that the focus position of the objective lens of the pickup 112 accords with the signal side of the CD 101. The rotation servo circuit 122 generates a rotation drive control signal corresponding to the reproduced clock signal received from the clock signal generating circuit 117 and the reference clock signal received from the crystal oscillator 119. The rotation servo circuit 122 supplies the rotation drive control signal to a spindle motor 113 so as to control the rotating operation of the spindle motor 113.
The tracking and thread servo circuit 121 generates a tracking control and drive signal corresponding to the tracking error signal received from the pickup 112 and supplies the tracking control and drive signal to the pickup 112 so as to control the tracking operation of the pickup 112. In addition, the tracking and thread servo circuit 121 generates a control signal for driving a moving unit that moves the pickup 112 in the radial direction of the CD 101. The microprocessor 126 generates a track position control signal corresponding to for example data of channels P and Q and supplies the signal to the tracking and thread servo circuit 121 so as to move the pickup 112. The tracking and thread servo circuit 121 controls the track position of the pickup 112 corresponding to for example an access command.
Next, a sub-code and data of channels P and Q will be described. A signal recorded on the CD is sampled at a sampling frequency of 44.1 kHz of which one sample or one word is composed of 16 bits. Each sample or word composed of 16 bits is divided into high order eight bits and low order eight bits as symbols. The error-correction-code encoding process and the interleaving process are performed for each symbol. Every 24 symbols of audio data are grouped as one frame. One frame is equivalent to six samples of each of left and right channels.
In the EFM modulating process, eight bits of each symbol are converted into 14 bits. FIG. 3 shows a data structure of one frame that has been EFM modulated. One frame 135 is composed of a synchronous pattern data region 131 of 24 channel bits, a sub-code region 132 of 14 channel bits, a program data region 133 of 12 symbols including program data D1 to D12, a parity data region 134 of 4 symbols including parity data P1 to P4, and other program regions 133 and 134. Each region or data portion is connected with three channel bits as connection bits. Thus, one frame 135 has a total of 588 channel bits.
FIG. 4 shows an arrangement of which individual regions and data portion of 98 frames are vertically and successively disposed. The interval of 98 frames shown in FIG. 4 is equivalent to a block of which a sub-code is completed. Thus, a block of 98 frames is referred to as a sub-code frame. The sub-code frame is composed of a frame synchronous pattern portion 136, a sub-code portion 137, and a data and parity portion 138. One sub-code frame is equivalent to 1/75 second of the reproducing time of a CD.
Sub-code data including data of channels P and Q supplied from the sub-code detecting circuit 118 shown in FIG. 2 is data recorded in the sub-code portion 137 shown in FIG. 4. FIG. 5 shows a detailed data structure of the sub-code frame in the sub-code portion 137. First two frames F01 and F02 are synchronous patterns S0 and S1 of the sub-code frame. As with the frame synchronous patterns, the synchronous patterns S0 and S1 are out-of-rule patterns of the EFM modulating process. The sub-code detecting circuit 118 shown in FIG. 2 detects the synchronous patterns S0 and S1 as a delimiter of a sub-code frame. In addition, eight bits of one symbol compose data of channels P to W of the sub-code. For example, data of channel P is composed of parts of S0 and S1 and P01 to P96.
The data of channel P of the sub-code has information that represents whether or not a program is present. The data of channel Q has absolute time information of the CD, time information of each program, and information of each program number (also referred to as track number), each program part number (also referred to as index number), and so forth. Thus, with the information of channel Q, a reproducing operation including, for example a program start position detecting operation can be controlled. In addition, with the information of channel Q displayed, the user can visually know what program number the current program has on the CD, the running time of the program, the absolute time, and so forth. In addition, data of six channels R to W of the sub-code is used for still pictures and texts of programs. A reproducing apparatus using data of channels R to W is referred to as a CD-graphics. The apparatus has been disclosed in for example U.S. Pat. No. 5,282,186.
To improve the operability of the CD reproducing apparatus, a function for browsing the contents of the CD is known. As an example of such a function, the top portion (for example, 15 seconds) of each program is successively reproduced. In commercially available CD players, such a function is called intro-scanning function or music-scanning function. With such a function, the user can quickly know the contents of programs recorded on the CD. Such a CD player has been disclosed as Japanese Utility Patent Laid-Open Publication No. 58-109886 (laid-open on Jul. 26, 1983).
The intro-scanning mode is accomplished using TOC data of the CD. As the TOC data, the start address of each program, the end address thereof, the first program number, the last program number, and so forth are recorded in the program management region (the read-in region 103) of the CD shown in FIG. 1. When the CD is loaded, the TOC data is read by the reproducing apparatus. The TOC data is stored in the memory of the apparatus. The pickup is moved to the start address of a program designated corresponding to the TOC data and the reproducing operation is performed for a predetermined time period (for example, 15 seconds). By repeating the pickup moving operation and the reproducing operation, the intro-scanning function is accomplished. However, this function is used for reproducing only the start portion of each program. Thus, the user cannot know the contents or features of each program.